.\" -*- nroff -*-
.\" Copyright 2013 Los Alamos National Security, LLC. All rights reserved.
.\" Copyright 2010 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" Copyright (c) 2020      Google, LLC. All rights reserved.
.\" $COPYRIGHT$
.TH MPI_Type_get_true_extent 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
.SH NAME
\fBMPI_Type_get_true_extent\fP, \fBMPI_Type_get_true_extent_x\fP \- Returns the true lower bound and extent of a data type's corresponding typemap, ignoring MPI_UB and MPI_LB markers.

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Type_get_true_extent(MPI_Datatype \fIdatatype\fP,
	MPI_Aint *\fItrue_lb\fP, MPI_Aint *\fItrue_extent\fP)
int MPI_Type_get_true_extent_x(MPI_Datatype \fIdatatype\fP,
	MPI_Count *\fItrue_lb\fP, MPI_Count *\fItrue_extent\fP)

.fi
.SH Fortran Syntax (see FORTRAN 77 NOTES)
.nf
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TYPE_GET_TRUE_EXTENT(\fIDATATYPE, TRUE_LB, TRUE_EXTENT, IERROR\fP)
	INTEGER	\fIDATATYPE, IERROR\fP
	INTEGER(KIND=MPI_ADDRESS_KIND) \fITRUE_LB, TRUE_EXTENT\fP
MPI_TYPE_GET_TRUE_EXTENT_X(\fIDATATYPE, TRUE_LB, TRUE_EXTENT, IERROR\fP)
	INTEGER	\fIDATATYPE, IERROR\fP
	INTEGER(KIND=MPI_COUNT_KIND) \fITRUE_LB, TRUE_EXTENT\fP

.fi
.SH Fortran 2008 Syntax
.nf
USE mpi_f08
MPI_Type_get_true_extent(\fIdatatype\fP, \fItrue_lb\fP, \fItrue_extent\fP, \fIierror\fP)
	TYPE(MPI_Datatype), INTENT(IN) :: \fIdatatype\fP
	INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(OUT) :: \fItrue_lb\fP, \fItrue_extent\fP
	INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP
MPI_Type_get_true_extent_x(\fIdatatype\fP, \fItrue_lb\fP, \fItrue_extent\fP, \fIierror\fP)
	TYPE(MPI_Datatype), INTENT(IN) :: \fIdatatype\fP
	INTEGER(KIND = MPI_COUNT_KIND), INTENT(OUT) :: \fItrue_lb\fP, \fItrue_extent\fP
	INTEGER, OPTIONAL, INTENT(OUT) :: \fIierror\fP

.fi
.SH INPUT PARAMETER
.ft R
.TP 1i
datatype
Data type for which information is wanted (handle).
.sp
.SH OUTPUT PARAMETERS
.ft R
.TP 1i
true_lb
True lower bound of data type (integer).
.TP 1i
true_extent
True size of data type (integer).
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
The \fItrue_lb\fP parameter returns the offset of the lowest unit of store that is addressed by the data type, that is, the lower bound of the corresponding typemap, ignoring MPI_LB markers. The \fItrue_extent\fP parameter returns the true size of the data type, that is, the extent of the corresponding typemap, ignoring MPI_LB and MPI_UB markers, and performing no rounding for alignment. For both functions, if either the \fItrue_lb\fP or \fItrue_extent\fP parameter cannot express the value to be returned (e.g., if the parameter is too small to hold the output value), it is set to MPI_UNDEFINED.
.sp
The \fItrue_extent\fP is the minimum number of bytes of memory necessary to hold a data type, uncompressed.
.sp
See § 4.1.8 of the MPI-3 standard for more detailed definitions of these parameters in relation to the typemap.

.SH FORTRAN 77 NOTES
.ft R
The MPI standard prescribes portable Fortran syntax for
the \fITRUE_LB\fP and \fITRUE_EXTENT\fP arguments only for Fortran 90. FORTRAN 77 users may use the non-portable syntax
.sp
MPI_Type_get_true_extent:
.sp
.nf
     INTEGER*MPI_ADDRESS_KIND \fITRUE_LB\fP
or
     INTEGER*MPI_ADDRESS_KIND \fITRUE_EXTENT\fP
.fi
.sp
MPI_Type_get_true_extent_x:
.sp
.nf
     INTEGER*MPI_COUNT_KIND \fITRUE_LB\fP
or
     INTEGER*MPI_COUNT_KIND \fITRUE_EXTENT\fP
.fi
.sp
where MPI_ADDRESS_KIND and MPI_COUNT_KIND are constants defined in mpif.h and give the length of the declared integer in bytes.

.SH ERRORS
Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.

